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AST_AXDISTANCE - Find the distance between two axis values

Description:
This routine returns a signed value representing the axis increment from axis value v1 to axis value v2.

For a simple Frame, this is a trivial operation returning the difference between the two axis values. But for other derived classes of Frame (such as a SkyFrame) this is not the case.

Invocation:
RESULT = AST_AXDISTANCE( THIS, AXIS, V1, V2, STATUS )
Arguments:
THIS = INTEGER (Given)
Pointer to the Frame.
AXIS = INTEGER (Given)
The index of the axis to which the supplied values refer. The first axis has index 1.
V1 = DOUBLE PRECISION (Given)
The first axis value.
V2 = DOUBLE PRECISION (Given)
The second axis value.
STATUS = INTEGER (Given and Returned)
The global status.
Returned Value:
AST_AXDISTANCE = DOUBLE PRECISION
The distance from the first to the second axis value.
Notes:
  • This function will return a "bad" result value (AST__BAD) if any of the input values has this value.

  • A "bad" value will also be returned if this function is invoked with STATUS set to an error value, or if it should fail for any reason.


next up previous 264
Next: AST_AXOFFSET - Add an increment onto a supplied axis value
Up: AST Routine Descriptions
Previous: AST_AXANGLE - Returns the angle from an axis, to a line through two points

AST A Library for Handling World Coordinate Systems in Astronomy
Starlink User Note 210
R.F. Warren-Smith & D.S. Berry
24th May 2011
E-mail:ussc@star.rl.ac.uk

Copyright (C) 2009 Science \& Technology Facilities Council